The present invention relates to a sensorless motor starting system to start a sensorless motor under optimal starting conditions in accordance with the characteristics thereof and a load to be driven.
A brushless motor, which comprises a permanent magnet rotor and a coil for generating a field and has a long service life with excellent noiseless and dustless characteristics, is used as a spindle motor to drive and rotate an optical disc such as CD (Compact Disc) or MD (Mini Disc) on its axis. Further, there is employed a sensorless motor rotatable by a coil-induced voltage instead of a Hall element signal in a brushless motor.
For example, in a conventional portable MD signal processing LSI using a sensorless motor as a spindle motor, spindle motor start parameters (phase switching time, phase switching number, drive voltage) are kept fixed, and it is impossible to adjust such start parameters.
There is known a case where, depending on a motor driver, the phase switching time and the phase switching number are adjusted on the motor driver side. In such a case, however, the operation is complicated and the loss in power consumption is rendered greater, since such adjustment is executed by supplying a servo output of the spindle motor as an analog signal to the motor driver.
In a sensorless motor starting system for driving an optical disc such as MD, CD or DVD (Digital Versatile Disc), it is requisite to achieve high-precision rotation of the sensorless motor at a desired speed with low power consumption by adjusting the start parameters (phase switching time, phase switching number, drive signal) in a manner to exactly conform with delicate characteristic changes of the sensorless motor or characteristic variations of the driver.
The present invention has been accomplished in view of the current circumstances of the sensorless motor starting system mentioned above. And it is an object of the invention to provide an improved sensorless motor starting system of a simplified structure which is capable of solving the problems relative to slight changes in the sensorless motor characteristics or variations in the driver characteristics by detecting the initial rotation state of the sensorless motor and executing fine adjustment of the start parameters directly in accordance with requirements, hence starting the sensorless motor under optimal target starting conditions while minimizing the power consumption in conformity with the type of the motor and the load to be driven.
According to one aspect of the present invention, there is provided a sensorless motor starting system which comprises a mode setting means for selectively setting either a start acceleration mode or a fixed frequency mode for the sensorless motor; an automatic parameter setting means for setting, in the sensorless motor, start parameters to specify the start-time driving conditions preset correspondingly to the motor characteristic and a load to be driven; an automatic motor starting means for starting the rotation of the sensorless motor in an automatic mode on the basis of the start-time driving conditions specified by the start parameters set by""the automatic parameter setting means; a start state decision means for making a decision as to whether the start state of the sensorless motor started by the automatic motor starting means is coincident or not with a target start state; and a start parameter setting mode change means for canceling the start executed by the automatic motor starting means when the result of the decision obtained from the start state decision means signifies a deviation of the sensorless motor start state from the target start state, and then changing the setting of the start parameters to a manual setting mode.
In the structure mentioned above, either a start acceleration mode or a fixed frequency mode is set selectively for the sensorless motor, and in case the start acceleration mode is selectively set, start parameters for specifying the start-time driving conditions preset correspondingly to the motor characteristics and the driven load are set by the automatic parameter setting means. Then the sensorless motor is started and rotated in the automatic mode on the basis of the start-time driving conditions specified by the start parameters set by the automatic parameter setting means, and a decision is made by the start state decision means as to whether the start state of the sensorless motor is coincident or not with the target start state.
And if the result of the decision signifies that the start state of the sensorless motor has a deviation from the target start state, the setting of the start parameters by the automatic starting means is canceled and then is changed to the automatic setting mode, whereby manual adjustment is executed in such a manner that the start parameters give the target start state to the sensorless motor. Thus, the sensorless motor is started by the simplified structure with low power consumption for the load under optimal target start conditions in response to slight changes in the sensorless motor characteristics or variations in the driver characteristics.
In the sensorless motor driving system mentioned above, the start parameters specify a phase switching time, a phase switching number and a drive signal.
Due to such means in the simplified structure, the spindle motor can be started under optimal target start conditions with low power consumption in response to slight changes in the motor characteristics or variations in the driver characteristics correspondingly to the motor characteristics and the kind of an optical disc to be driven.
The above and other features and advantages of the present invention will become apparent from the following description which will be given with reference to the illustrative accompanying drawings.